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OpenInsider vs ShareSeer vs Form4API
Updated 2026-07-26. By Theodor Nielsen, founder of Form4API. Competitor features checked July 2026 from their public pages.
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OpenInsider is a free web screener for browsing SEC Form 4 filings by hand. ShareSeer is a web tracker that adds email alerts and a Chrome extension (~$49/mo for premium). Form4API is a developer API — parsed Form 4 data as JSON, with webhooks, SDKs, and an MCP server. If a person is browsing, use OpenInsider; if code or an AI agent is consuming the data, use Form4API.
The real distinction: a tool for people vs an API for code
These three are often lumped together as "insider trading tools," but they answer different questions. OpenInsider and ShareSeer are end-user websites — you open a browser, look at recent filings, and maybe set an alert. Form4API is developer infrastructure — your program calls it and gets back structured JSON to act on.
That difference decides everything else: whether there is a documented API, whether you get real-time webhooks, whether fields like the 10b5-1 plan flag are queryable, and whether an AI agent can pull the data via MCP.
OpenInsider — the free screener
OpenInsider is a long-running, free, ad-supported web screener for U.S. Form 4 filings. It has genuinely useful prebuilt screens — latest purchases and sales, $25k+ CEO/CFO buys, cluster buys, weekly and monthly top buys — plus insider profiles and CSV export links on its lists (as of July 2026).
What it is not is a developer platform: there is no official API, no webhooks, and no structured fields like a 10b5-1 flag or forward returns. Third-party projects scrape it and expose unofficial APIs, but those inherit the fragility of scraping. For manual research it is excellent and free; for anything programmatic it is the wrong shape.
When a free tool is the right call
Being honest about where the free tools win is the point of this page. Use OpenInsider or ShareSeer when:
- A human is doing the looking. One-off research, checking recent buys at a ticker, casually following a handful of insiders — a website is faster than writing code.
- You want zero setup and zero cost. OpenInsider asks for nothing; ShareSeer's free tier and extension cover a lot of casual use.
- You do not need structured data or delivery. If you are not building on it, the absence of an API and webhooks does not matter.
Reach for Form4API the moment the consumer is code, not a person — a strategy, a screener you are building, an alert bot, a backtest, a spreadsheet pipeline, or an AI agent. The free tier is 500 requests/day, no card.
Side-by-side
| Dimension | OpenInsider | ShareSeer | Form4API |
|---|---|---|---|
| What it is | Free web screener | Web tracker + alerts | Developer REST API |
| Best for | Browsing filings by hand | Following names, email alerts | Building apps, agents, backtests |
| Official API | No (third-party scrapers only) | Not documented | Yes — REST + SDKs (Python/JS) |
| Real-time push | No | Email alerts (premium) | HMAC-signed webhooks |
| AI / MCP | No (unofficial 3rd-party MCP exists) | No | Official MCP server (~30 tools) |
| 10b5-1 flag | Not exposed | Not exposed | Queryable field |
| Post-trade returns | No | No | Enriched on open-market buys |
| Price | Free (ad-supported) | ~$49/mo (annual) for premium | Free 500/day; Pro $49/mo |
OpenInsider and ShareSeer details sourced from their public pages as of July 2026; verify current terms before deciding. See also our API-to-API comparisons (sec-api.io, EODHD, EdgarTools).
Frequently asked questions
Does OpenInsider have an API?
OpenInsider does not offer an official API — it is a free, ad-supported web screener you use by hand, with CSV export links on its lists (as of July 2026). Several third-party projects scrape OpenInsider and expose the data as an unofficial API, but those depend on scraping a site that can change or block at any time. If you need a supported, structured API with a stable contract, that is what Form4API provides: parsed Form 4 data as JSON with an OpenAPI spec, SDKs, and webhooks.
What is the difference between OpenInsider and Form4API?
They serve different users. OpenInsider is a website for a person to browse SEC Form 4 filings — prebuilt screens, insider profiles, CSV downloads, all free. Form4API is infrastructure for a developer to build on: a REST API and SDKs that return parsed, amendment-aware transactions with 10b5-1 flags and forward returns, plus real-time webhooks and an MCP server for AI agents. If you are clicking around to research trades, OpenInsider is great; if you are writing code, wiring an alert bot, or feeding an AI agent, you want an API.
Is ShareSeer better than OpenInsider?
They overlap but differ. Both track SEC insider filings; ShareSeer adds email alerts, a Chrome extension, and premium features like Excel financial-statement downloads for about $49/month billed annually (as of July 2026), while OpenInsider is fully free and screener-focused. Neither publishes a documented developer API. For a non-developer who wants alerts and a polished UI, ShareSeer is a reasonable paid step up; for programmatic access, both fall short of a real API.
When should I use a free tool instead of Form4API?
Use OpenInsider or ShareSeer when a human just needs to look things up — one-off research, eyeballing recent buys at a ticker, or casually following a few insiders. There is no reason to call an API for that. Reach for Form4API when the consumer is code rather than a person: a trading strategy, a screener you are building, an alert bot, a spreadsheet pipeline, or an AI agent — anything that needs structured data, real-time delivery, or fields like the 10b5-1 flag that the free UIs do not expose.